The apparatus disclosed in Applicant's U.S. Pat. No. 4,177,941 advanced the art over that in existence prior thereto. However, such apparatus was not completely satisfactory for Applicant's ultimate purposes. For example, the stirring means for agitating the dust in order to facilitate its movement into the openings in the metering disk is complex and is disposed in a chamber exposed to the ambient atmosphere. Accordingly, ambient air can be contaminated by the agitation of the dust, and transfer of the dust to the metering disk can be erratic. In addition, the driving motor is mounted above the metering disk so that lubricant for the motor and the interconnecting drive mechanism can contaminate the metering disk and the dust carried thereby. Further, the bearing beneath the dust chamber which supports the stirring means is exposed to the dust in the chamber, necessitating periodic cleaning to prevent jamming. Also, the changing of the metering disk in order to provide variations in the amount of dust being delivered involves a virtually complete disassembly of the apparatus.
Accordingly, a primary object of this invention has been the provision of a relatively simple dust generator or dust delivery apparatus having a dust containing hopper which is substantially airtight and the interior of which is periodically exposed to a pulse of gas under pressure which agitates the dust therein.
A further object of this invention is the provision of an apparatus, as aforesaid, to provide a mechanism which can be readily and quickly disassembled for the purpose of changing metering disks and which works well with both free-flowing and non-free-flowing powders.
A further object of the invention is the provision of an apparatus, as aforesaid, in which the bearings are not continuously exposed to the dust in the dust chamber and therefore need not be frequently cleaned to prevent jamming.
A further object of this invention is the provision of an apparatus, as aforesaid, wherein the entire driving mechanism is located below the metering disk to avoid any contamination thereof by lubricants and to simplify the changing of the gear train in order to effect variations in the rotational speed of the metering disk.